<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Simple XMLHttpRequest</title>
<script type="text/javascript">
var xmlHttp;
function createXMLHttpRequest() {
    if (window.ActiveXObject) {
        xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    }else if (window.XMLHttpRequest) {
        xmlHttp = new XMLHttpRequest();
    }
}
function startRequest() {
	createXMLHttpRequest();
    xmlHttp.onreadystatechange = handleStateChange;
    xmlHttp.open("GET", "simpleResponse.xml", true);
    xmlHttp.send(null);
}
    
function handleStateChange() {
    if(xmlHttp.readyState == 4) {
        if(xmlHttp.status == 200) {
            alert("服务器返回： " + xmlHttp.responseText);
        }
    }
}
</script>
</head>
<body>
    <form action="#">
        <input type="button" value="开始异步请求" 
onclick="startRequest();"/>
    </form>
</body>
</html>
